My i386 system, running a -current kernel from yesterday's sources
(4.99.35) and userland from about a month ago just froze for about 30
seconds.  I was in X (using Xorg-modular from pkgsrc); moving the mouse
didn't work, and the window manager's clock stopped ticking.  Here's the
content of /var/log/messages just before and after the freeze.  (I think
that the freeze continued for at least 10 seconds longer than is implied
by the "11:49:37" timestamps.)

Nov 11 11:49:14 apb-laptoy /netbsd: pms0: pms_input: unusual delay (0.050026 s),
 scheduling reset
Nov 11 11:49:37 apb-laptoy /netbsd: pckbport: command timeout
Nov 11 11:49:37 apb-laptoy /netbsd: wpi0: fatal firmware error
Nov 11 11:49:37 apb-laptoy /netbsd: pms_disable: command error
Nov 11 11:49:37 apb-laptoy /netbsd: acpiec0: EcWrite: timeout waiting for EC to
process write command
Nov 11 11:49:37 apb-laptoy /netbsd: ACPI Exception (evregion-0521): AE_ERROR, Re
turned by Handler for [EmbeddedControl] [20060217]
Nov 11 11:49:37 apb-laptoy /netbsd: ACPI Error (psparse-0626): Method parse/exec
ution failed [\_SB_.C002.C003.C005.C18C] (Node 0xc1ea4f80), AE_ERROR
Nov 11 11:49:37 apb-laptoy /netbsd: ACPI Error (psparse-0626): Method parse/exec
ution failed [\_TZ_.C2FF] (Node 0xc1ea92e0), AE_ERROR
Nov 11 11:49:37 apb-laptoy /netbsd: ACPI Error (psparse-0626): Method parse/exec
ution failed [\_TZ_.C30B._OFF] (Node 0xc1eabfe0), AE_ERROR
Nov 11 11:49:37 apb-laptoy /netbsd: acpiec0: EcWrite: timeout waiting for EC to
process write command
Nov 11 11:49:37 apb-laptoy /netbsd: ACPI Exception (evregion-0521): AE_ERROR, Re
turned by Handler for [EmbeddedControl] [20060217]
Nov 11 11:49:37 apb-laptoy /netbsd: ACPI Error (psparse-0626): Method parse/exec
ution failed [\_SB_.C002.C003.C005.C18C] (Node 0xc1ea4f80), AE_ERROR
Nov 11 11:49:37 apb-laptoy /netbsd: ACPI Error (psparse-0626): Method parse/exec
ution failed [\_TZ_.C2FF] (Node 0xc1ea92e0), AE_ERROR
Nov 11 11:49:37 apb-laptoy /netbsd: ACPI Error (psparse-0626): Method parse/exec
ution failed [\_TZ_.C30A._ON_] (Node 0xc1ea9080), AE_ERROR
Nov 11 11:49:37 apb-laptoy /netbsd: acpiec0: EcRead: timeout waiting for EC to p
rocess read command
Nov 11 11:49:37 apb-laptoy /netbsd: ACPI Exception (evregion-0521): AE_ERROR, Re
turned by Handler for [EmbeddedControl] [20060217]
Nov 11 11:49:37 apb-laptoy /netbsd: ACPI Exception (dswexec-0568): AE_ERROR, Whi
le resolving operands for [AE_NOT_CONFIGURED] [20060217]
Nov 11 11:49:37 apb-laptoy /netbsd: ACPI Error (psparse-0626): Method parse/exec
ution failed [\_TZ_.C305] (Node 0xc1ea9240), AE_ERROR
Nov 11 11:49:37 apb-laptoy /netbsd: ACPI Error (psparse-0626): Method parse/exec
ution failed [\_TZ_.TZ3_._TMP] (Node 0xc1eab9a0), AE_ERROR
Nov 11 11:49:37 apb-laptoy /netbsd: acpitz3: failed to evaluate _TMP

I suspect a mouse driver problem.  Slightly older kernels (possibly
around 4.99.20 or 4.99.25) with exactly the same Xorg userland have
exhibited a problem in which the mouse gets very jerky or entirely stops
working, but comes right if I flip to a text console via alt-control-F1
and then flip back to the X console via alt-control-F5.

--apb (Alan Barrett)